The present invention relates to a method for producing image using a photothermographic material well applicable to an image producing system typically for medical diagnosis.
As general image producing systems, a variety of hard copy systems making use of pigments or dyes are prevailing, which are typified by an ink jet printer and electronic photographing apparatus, for example. These image producing systems are, however, not satisfactory for medical use in which advanced levels of fine depiction, sharpness and graininess are required. A blue-black tone for facilitating diagnoses is preferred in medical use, and also an image producing system which produces only a few waste process solution is preferred from the viewpoint of environmental preservation and space saving.
In relation to an image producing system for medical use meeting the foregoing demands, a technology utilizing a photothermographic material has been developed. This technology has been successful in affording efficient light exposure with a laser image setter or laser imager, providing a sharp and clear black image with a high resolution, and providing a simpler and environment-conscious image producing system using no chemical for treating the solution or the like.
Examples of the image producing system making use of photothermographic material and in particular making use of organic silver salt are disclosed, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075 and xe2x80x9cThermally Processed Silver Systemsxe2x80x94Axe2x80x9d by D. Klosterboer, Imaging Processes and Materials, Neblette""s 8th ed., edited by Sturge, V. Walworth and A. Shepp, Chapter 9, p.279, (1989).
The photothermographic material generally has a photosensitive layer comprising a silver halide as a photocatalyst, a reducible silver salt such as an organic silver salt, a reducing agent, a binder, and an optional color toner for controlling color tone of silver image, all of which being dispersed in a binder matrix. The photothermographic material having such photosensitive layer produces blackened silver when heated, after light exposure, to a high temperature (e.g. 80xc2x0 C. or above) through redox reaction of the silver halide or reducible silver salt (acts as an oxidizing agent) with the reducing agent. The redox reaction is promoted by a catalytic action of silver halide composing a latent image generated by the exposure, so that the monotone silver image is formed in the exposed area. An image producing system utilizing such organic silver salt can provide an image quality and tone satisfiable for medical diagnosis.
The image producing system using the conventional photothermographic material is, however, liable to be affected by environmental conditions during the exposure and development. For example, a problem has resided in that a stable finish cannot be expected because of fluctuation in the temperature and humidity depending on the installation environment of an image producing apparatus or frequency of the exposure and development.
Considering such problems in the conventional technology, it is therefore an object of the present invention to provide a method for producing image using a photothermographic material ensuring stable finish irrespective of the installation environment of an image producing apparatus or of fluctuations in the temperature or humidity inside the apparatus during the operations.
The present inventors found after extensive investigations for achieving the above object that an image with a constant quality can be producible irrespective of the environmental conditions by correctively controlling the exposure output according to a temperature profile of a photothermographic material within an image producing apparatus, which led us to propose the present invention.
That is, the present invention provides a method for producing image using a photothermographic material in which the photothermographic material is exposed with a laser light using an image producing apparatus having a recording section and heat developing section, and then developed by heating, the photothermographic material containing at least elsewhere on one plane of the support at least one kind of photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ion and a binder; characterized in that the photosensitive silver halide contains an iridium compound, and the image producing apparatus has an exposure corrective control means for correctively controlling the exposure output according to a temperature profile of the photothermographic material within said apparatus.
In a method for producing image of the present invention, it is preferable that the exposure corrective control means measures the temperature of the photothermographic material immediately before entering the heat developing section and correctively controls the output of the laser exposure based on the measured values. More specifically, the corrective control is preferably effected by the exposure corrective control means so as to lower the laser output as the temperature immediately before entering the heat developing section rises, and so as to raise the laser output as the temperature decreases. It is also preferable to provide a cooling section in the successive stage of the heat developing section, and the exposure corrective control means measures the temperature at the entrance of the cooling section so as to effect the corrective control of the output of the laser exposure according to the obtained value. More specifically, the corrective control is preferably effected by the exposure corrective control means so as to lower the laser output as the temperature at the entrance of the cooling section rises and so as to raise the laser output as the temperature decreases, and so as to raise the laser output as the image density increases and so as to lower the laser output as the image density decreases.
In a method for producing image of the present invention, it is in particular preferable to combine the corrective control such that lowering the laser output as the temperature immediately before entering the heat developing section rises and raising the laser output as the temperature decreases, with the corrective control such that lowering the laser output as the temperature at the entrance of the cooling section rises and raising the laser output as the temperature decreases. It is preferable to further combine a corrective control such that lowering the laser output as the temperature of a stacking zone and such that raising the laser output as the temperature decreases.
The photosensitive silver halide used for the present invention preferably contains an iridium compound selected from the group consisting of hexachloroiridium, hexammineiridium, trioxalatoiridium, hexacyanoiridium and pentachloronitrosyliridium. Amount of addition of the iridium compound is preferably from 1xc3x9710xe2x88x928 to 1xc3x9710xe2x88x923 mol per one mol of silver halide, and more preferably from 1xc3x9710xe2x88x927 to 5xc3x9710xe2x88x924 mol.